content: /*
   * Copyright 2017 David Karnok
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package hu.akarnokd.reactive4javaflow.impl.schedulers;
  
  import hu.akarnokd.reactive4javaflow.*;
  import hu.akarnokd.reactive4javaflow.functionals.AutoDisposable;
  import hu.akarnokd.reactive4javaflow.impl.VH;
  
  import java.lang.invoke.*;
  import java.util.Objects;
  import java.util.concurrent.*;
  
  public final class SingleSchedulerService implements SchedulerService, ThreadFactory {
  
      final String namePrefix;
  
      final int priority;
  
      final boolean daemon;
  
      long index;
      static final VarHandle INDEX = VH.find(MethodHandles.lookup(), SingleSchedulerService.class, "index", Long.TYPE);
  
      ScheduledExecutorService exec;
      static final VarHandle EXEC = VH.find(MethodHandles.lookup(), SingleSchedulerService.class, "exec", ScheduledExecutorService.class);
  
      static final ScheduledExecutorService SHUTDOWN;
  
      static {
          SHUTDOWN = Executors.newScheduledThreadPool(0);
          SHUTDOWN.shutdown();
      }
  
      public SingleSchedulerService(String namePrefix, int priority, boolean daemon) {
          this.namePrefix = namePrefix;
          this.priority = priority;
          this.daemon = daemon;
          ScheduledExecutorService b = Executors.newScheduledThreadPool(1, this);
          ((ScheduledThreadPoolExecutor)b).setRemoveOnCancelPolicy(true);
          EXEC.setRelease(this, b);
      }
  
      @Override
      public Thread newThread(Runnable r) {
          Thread thread = new Thread(r, namePrefix + "-" + ((long)INDEX.getAndAdd(this, 1) + 1));
          thread.setPriority(priority);
          thread.setDaemon(daemon);
          return thread;
      }
  
      @Override
      public AutoDisposable schedule(Runnable task) {
          Objects.requireNonNull(task, "task == null");
          ScheduledExecutorService exec = (ScheduledExecutorService)EXEC.getAcquire(this);
          WorkerTask wt = new WorkerTask(task, null);
          try {
              Future<?> f = exec.submit((Callable<Void>)wt);
              wt.setFutureNoCancel(f);
              return wt;
          } catch (RejectedExecutionException ex) {
              FolyamPlugins.onError(ex);
          }
          return REJECTED;
      }
  
      @Override
      public AutoDisposable schedule(Runnable task, long delay, TimeUnit unit) {
          Objects.requireNonNull(task, "task == null");
          ScheduledExecutorService exec = (ScheduledExecutorService)EXEC.getAcquire(this);
          WorkerTask wt = new WorkerTask(task, null);
          try {
              Future<?> f = exec.schedule((Callable<Void>)wt, delay, unit);
              wt.setFutureNoCancel(f);
              return wt;
          } catch (RejectedExecutionException ex) {
              FolyamPlugins.onError(ex);
          }
          return REJECTED;
      }
  
      @Override
      public AutoDisposable schedulePeriodically(Runnable task, long initialDelay, long period, TimeUnit unit) {
          Objects.requireNonNull(task, "task == null");
          if (period <= 0L) {
              return SchedulerService.super.schedulePeriodically(task, initialDelay, period, unit);
          }
          ScheduledExecutorService exec = (ScheduledExecutorService)EXEC.getAcquire(this);
          WorkerTask wt = new WorkerTask(task, null);
          try {
              Future<?> f = exec.scheduleAtFixedRate(wt, initialDelay, period, unit);
              wt.setFutureNoCancel(f);
              return wt;
          } catch (RejectedExecutionException ex) {
              FolyamPlugins.onError(ex);
          }
          return REJECTED;
      }
  
      @Override
      public Worker worker() {
          return new ScheduledExecutorServiceWorker((ScheduledExecutorService)EXEC.getAcquire(this));
      }
  
      @Override
      public void start() {
          ScheduledExecutorService b = null;
          for (;;) {
              ScheduledExecutorService a = (ScheduledExecutorService)EXEC.getAcquire(this);
              if (a != SHUTDOWN) {
                  if (b != null) {
                      b.shutdown();
                  }
                  return;
              }
              if (b == null) {
                  b = Executors.newScheduledThreadPool(1, this);
                  ((ScheduledThreadPoolExecutor)b).setRemoveOnCancelPolicy(true);
              }
              if (EXEC.compareAndSet(this, a, b)) {
                  return;
              }
          }
      }
  
      @Override
      public void shutdown() {
          ((ScheduledExecutorService)EXEC.getAndSet(this, SHUTDOWN)).shutdownNow();
      }
  }
  